The present invention relates to a gearshift device for switching a gear position of an automatic transmission.
In the prior art, a so-called by-wire gearshift device which is a gearshift device mechanically separated from an automatic transmission in a vehicle is widely used. The gearshift device detects the position of a gearshift lever serving as a gearshift means operated by a user as an electric signal and electronically shifts the gear position (connection state) of the automatic transmission based on the detection signal. A mechanical structure such as link mechanism is thus unnecessary. This reduces limitations on the location of the gearshift device and facilitates miniaturization.
Further miniaturization of the gearshift device is required to provide more space for the passenger compartment, reduce the space occupied by the gearshift device, and other reasons. To satisfy such a requirement, a rotary type gearshift knob, which is rotatable relative to an object on which it is arranged, may be used as the gearshift means in place of the above-described gearshift lever, as described in, for example, Japanese Laid-Open Patent Publication No. 2002-254946. Such a knob is merely rotated about a single axis. Thus, less space is occupied by the gearshift device compared to the above-described gearshift lever. More specifically, when using a gearshift lever, a gearshift gate would be necessary to guide the lever in a predetermined direction, whereas such guiding means is unnecessary when using the rotary gearshift knob.
The gearshift device described in the above publication includes a lock device for restricting rotation of the gearshift knob and serving as an erroneous operation prevention device for preventing erroneous operation of the gearshift knob. The lock device includes an engagement member which, in cooperation with the projection and retraction of a solenoid plunger, moves between an engaged position to engage an engagement portion of the gearshift knob and a disengaged position disengaged from the engagement portion. Rotation of the gearshift knob is restricted when the engagement member is held at the engaged position. Rotation of the gearshift knob is permitted when the engagement member is held at the disengaged position.
For instance, when the gearshift knob is held at a parking position, the engagement member holds the gearshift knob at the engaged position to restrict rotation of the gearshift knob. When driving the vehicle, the rotation restriction of the gearshift knob is canceled in the following manner. When depression of a brake pedal is detected in a state in which the engine has been started, the solenoid is driven to move the engagement member from the engaged position to the disengaged position. The gear position of the automatic transmission is then shifted to a position corresponding to the position of the gearshift knob when the knob is rotated.
In the gearshift device described in the above publication, the rotation restriction of the gearshift knob cannot be canceled by just operating the knob. However, for example, when the brake pedal is inadvertently depressed, the gearshift knob may be unintentionally rotated. The gearshift knob may also be rotated in such an unintentional manner when the rotation of the gearshift knob cannot be restricted for one reason or the other such as failure of the solenoid. Therefore, in the gearshift device of the above publication, there still remains the possibility of erroneous operation of the gearshift knob. There is thus still room for improvement in this respect.